Method of making display devices

ABSTRACT

A method of making a gas discharge display device comprising assembling the component parts of the device and providing a tabulation through which the device can be filled with the desired gas. A capsule containing an antisputtering agent such as mercury is mounted within the tabulation, along with suitable means by which it may be heated. The device is suitably baked out and otherwise preliminarily processed; the desired gas is introduced; and the tubulation is sealed off with the capsule remaining therein. After any other processing steps are carried out as required, the material is freed from the capsule, and, with the entire assembly heated to a suitable temperature to cause the anitsputtering agent to enter the working area of the device, the tubulation is sealed off at an area close to the device itself and with the capsule within the portion of the tubulation which is removed.

United States Patent [72] Inventor George A. Kupsky Miliord,N.J. [21]Appl. No. 764,983 [22] Filed Oct. 2, 1968 [45] Patented May 25, 1971[73] Assignee Burroughs Corporation Detroit, Mich.

(54} METHOD OF MAKING DISPLAY DEVICES 6 Claims, 2 Drawing Figs.

[52] US. Cl 316/20, 316/24 [51] lnt.Cl H0lj 9/38 [50] Field of Search316/20, 24, 26,17, 18; 141/59 [56] References Cited UNITED STATESPATENTS 1,565,579 12/1925 Mac Rae 316/20X 1,826,383 10/1931 Smalley.....316/20X 1,841,034 1/1932 lves 316/20X 2,449,493 9/1948 Longini 316/20X2,755,159 7/1956 Bemuretal. 2,991,387 7/1961 McCawley ABSTRACT: A methodof making a gas discharge display device comprising assembling thecomponent parts of the device and providing a tabulation through whichthe device can be filled with the desired gas. A capsule containing anantisputtering agent such as mercury is mounted within the tabulation,along with suitable means by which it may be heated. The device issuitably baked out and otherwise preliminarily processed; the desiredgas is introduced; and the tubulation is sealed 0E with the capsuleremaining therein. After any other processing steps are carried out asrequired, the material is freed from the capsule, and, with the entireassembly heated to a suitable temperature to cause the anitsputteringagent to enter the working area of the device, the tubulation is sealedoff at an area close to the device itself and with the capsule withinthe portion of the tubulation which is removed.

PATENTEU m2 5 19m INVENTOR. GEORGE A. KUPSKY mm gig ATTORNEY METHOD OFMAKING DISPLAY DEVICES BACKGROUND OF THE INVENTION It has becomestandard practice in cold cathode display devices to utilize argon andneon and the like as the preferred medium for providing glow discharge,and, ever since .I. H. McCauleys invention, it has become good practice,in addition, to provide a small quantity of mercury vapor to minimizecathode sputtering. Display tubes of the type having relatively largeenvelopes which contain relatively large cathode characters such asnumerals, letters, or the like, have utilized these features and havebecome commercially successful. In tubes of this type, the mercury isprovided in a capsule which carries a heating wire and is permanentlymounted within the tube with the heating wire connected to two tubepins. The mcrcury is released from the capsule at a desired stage in themanufacturing process by means of heat generated by current flow throughthe heating wire. When the mercury is released, its vapor readily fillsthe tube envelope. In this type of tube, tube pins are provided for ananode, for each of ten cathodes, and for two decimal points, and, inaddition, two extra tube pins are required for connection to the capsuleheating wire. Moreover, space must be available inside the envelope forthe mercury capsule.

For a long time, there has been a need for a display device of the flatpanel type which includes a large number of tiny cells formed in aunitary panel and utilizing cold cathodes and gaseous glow. Thesedevices use a gas of the type described above, and, in addition, requiremercury to minimize cathode sputtering. However, because of the type ofconstruction used in these devices and because of the small size of thecells, known procedures for introducing the gases and for introducingthe mercury are not satisfactory. For example, pins are not availablefor providing heating current for a capsule, and space is not availablein the device for a mercury capsule.

SUMMARY OF THE INVENTION Briefly, the invention comprises a methodmaking a gas discharge display device including the steps of assemblingthe parts of the device, baking out the device, introducing an ionizablegas into the device aging the electrodes of the device, introducing anantisputtering agent which has relatively high molecular weight andvaporization temperature, treating the device to cause theanitsputtering agent to vaporize and enter all portions of the device,and then sealing the device.

DESCRIPTION OF THE DRAWING FIG. I is a perspective view of a displaydevice prepared according to the invention; and

FIG. 2 is a sideview of the device of FIG. I and apparatus used in themanufacture thereof.

DESCRIPTION OF THE-PREFERRED EMBODIMENTS The principles of the inventionare applicable to display devices of different types. However, forpurposes of illustration, only one type of device, a flat panel device,is shown and described. Panel devices of this type are illustrated indetail in a concurrently filed application of G. A. Kupsky.

A display device embodying the invention, shown in FIG. I, includes acentral plate of insulating material such as glass or ceramic which isprovided with rows and columns of apertures or cells 30. Top and bottomglass cover plates 40 and 50 are secured to the center plate 20 withparallel row electrodes 60 between bottom'plate 50 and plate 20, andparallel column electrodes 70 between top plate 40 and center plate 20.Each row electrode 60 is aligned with a row of cells 30, and each columnelectrode 70 is aligned with a column of cells 30, and a cell is locatedat each crossing of a row electrode and a column electrode. In deviceI0, the row electrodes 60 are cathodes, and the column electrodes areanodes. Plates 20, 40, and 50 are preferably rectangular, and the-rowand column conductors 60 and 70 extend beyond the edges of the plates sothat electrical connection can be made to them.

In one typical panel 10, the central plate 20 is about 1 mm. inthickness, the top and bottom plates are about I to 3 mm. in thickness,and the cells are about 0.04 inch in diameter at a density of abouttwelve cells per linear inch. The conductors 60 and 70 are about 0.05inch wide and about 5 mils thick.

In manufacturing device 10, the various glass plates are provided withplate 40 carrying a glass tubulation in which is positioned a smallglass capsule which contains a tiny droplet of mercury 92. The capsule90 is supported by a wire conductor 100 which is wrapped around it andhas its ends extending through the wall of the capsule for subsequentconnection outside the capsule to a source of power 106.

With the glass plates and electrodes assembled and held togethermechanically, the various plates are sealed together along their edgesby means of a glass frit or the like to provide a gastight seal.

Next, the panel is pumped out and baked out by way of the tubulation 80,and it is filled with a gas suitable for sustaining cathode glow. Gasessuch as argon and neon are suitable, with one satisfactory gas mixturecomprising about 5 percent argon, percent neon, and a trace of krypton.The gas pressure is in the range of about 40 to about 80 Torr at roomtemperature. After the panel is baked out and then filled with its gas,the tubulation 80 is sealed off below the mercury capsule as at 120. Thepanel is then aged by cyclically firing each of the rows of cells inorder, with about 50 to about ma. of current flowing per row of cells.This aging step is carried out for a few hours.

Next, the mercury is released from its capsule 90 by means of heatapplied to the capsule to cause it to crack and release the mercury. Thenecessary heat is generated by current flow in conductor 100. If thedevice 10 is not at an elevated temperature, the mercury initiallydeposits on the wall of the tubulation above the capsule 90, and,according to the invention, in order to force the mercury into all ofthe cells 30 of the panel, the panel is baked in an oven at about 200 C.for several hours. With the panel held at this temperature, the portionof the tubulation containing the mercury capsule is removed, and thetubulation is sealed off at 130. The first aging step is then repeated.

If desired in the foregoing process, the device 10 may be heated toabout 200 C. before the mercury is released from its capsule, and thenwhen the mercury is released, it travels into the cells 30 directlywithout first condensing in the tubulation.

It is customary to use two or more aging steps with gas devices asdescribed; however, this is not a requirement and one step could beused.

It will be clear to those skilled in the art that the capsule 90 couldbe made of metal, and it could be heated by induction. It could also beof a material which can absorb infrared radiation, such radiation thenbeing used for heating and breaking the capsule. Other modifications mayalso be made within the scope of the invention.

1 claim:

1. A method of manufacturing a display tube of the type including aplurality of relatively small gas-filled cells comprising the steps ofmounting and enclosing electrodes within an envelope having an exhausttubulation, the electrodes having portions associated with each of saidcells,

placing a supply of vaporizable material at a point within saidtubulation, said material being physically immobilized and preventedfrom vaporizing and entering said tubulation and said tube during theprocessing steps associated with assembling said tube,

exhausting the atmosphere of said envelope through said tubulation,

inserting a gas into said envelope,

sealing said tubulation beyond the point where said vaporizable materialis located,

releasing said vaporizable material into said tubulation, and

heating said envelope and said tubulation to cause the vapor of saidmaterial to penetrate into said cells.

2. The method set forth in claim 1 further including the step ofremoving the tubulation beyond the point of the second seal and alsoremoving the remainder of the vaporizable material.

3. The method set forth in claim 1 wherein the step of placing a supplyof vaporizable material in the tubulation involves placing a sealedcapsule containing the vaporizable material together with an attachedwire in said tubulation, and wherein the step of activating saidvaporizable material involves passing a current through said attachedwire to heat the enclosed vaporizable material and crack said capsule.

4. The method defined in claim 1 and including, at a convenient timeafter sealing said tubulation, the step of aging said tube by applyingvoltages to said electrodes according to a predetermined program. v

5. The method defined in claim 1 and including the step of sealing saidtubulation a second time at a region between said envelope and the pointat which said vaporizable material was originally placed.

6. The method defined in claim 1 wherein said vaporizable material ismercury.

1. A method of manufacturing a display tube of the type including aplurality of relatively small gas-filled cells comprising the steps ofmounting and enclosing electrodes within an envelope having an exhausttubulation, the electrodes having portions associated with each of saidcells, placing a supply of vaporizable material at a point within saidtubulation, said material being physically immobilized and preventedfrom vaporizing and entering said tubulation and said tube during theprocessing steps associated with assembling said tube, exhausting theatmosphere of said envelope through said tubulation, inserting a gasinto said envelope, sealing said tubulation beyond the point where saidvaporizable material is located, releasing said vaporizable materialinto said tubulation, and heating said envelope and said tubulation tocause the vapor of said material to penetrate into said cells.
 2. Themethod set forth in claim 1 further including the step of removing thetubulation beyond the point of the second seal and also removing theremainder of the vaporizable material.
 3. The method set forth in claim1 wherein the step of placing a supply of vaporizable material in thetubulation involves placing a sealed capsule containing the vaporizablematerial together with an attached wire in said tubulation, and whereinthe step of activating said vaporizable material involves passing acurrent through said attached wire to heat the enclosed vaporizablematerial and crack said capsule.
 4. The method defined in claim 1 andincluding, at a convenient time after sealing said tubulation, the stepof aging said tube by applying voltages to said electrodes according toa predetermined program.
 5. The method defined in claim 1 and includingthe step of sealing said tubulation a second time at a region betweensaid envelope and the point at which said vaporizable material wasoriginally placed.
 6. The method defined in claim 1 wherein saidvaporizable material is mercury.